Fluorescence histochemical methodology is a rapidly developing research field of utmost importance for amine research. Our research team has contributed to the major developments in this field with grant support from NIH. But it is clear that vast possibilities within fluorescence histochemistry are still unexplored. In this light, the sensitivity of our fluorescence methods for investigating monoamines in single cells exceed, by far, that of all other available analytical techniques. Our immediate research objectives are to develop or exploit (1) New histochemical methods to visualize amine transmitters: This research is based on a continuous, extensive, and systematic screening of various carbonyl compounds for their capacity to form fluorophores with biogenic monamines and their congeners. This screening has already resulted in the uniquely sensitive glyoxylic acid method for delineating catecholamine neuron systems in their entirety. All the factors determining fluorescence yield are studied in detail, e.g., the reaction pathways and a newly discovered fluorescence enhancing phenomenon that occurs in the protein matrix, also in cells. (2) Novel methods for differentiating between closely related compounds: For this purpose, we will attempt to develop highly selective techniques that permit visualization of individual biogenic compounds and to elaborate methods that readily permit discrimination of closely related compounds (e.g., monoamines and their amino acid precursors). (3) Methods for improved visualization of indolamines: In theory, several modifications of the formaldehyde reaction, as well as the glyoxylic acid reaction, are very sensitive for visualizing serotonin and related indolamines. On the basis of these techniques, we are now attempting to develop more sensitive methods for the visualization of indolamine neurons--the great demand for such methods being indisputable. (4) Neuroanatomical applications: The new glyoxylic acid method has opened up entirely new opportunities for detailed investigations of the organization of catecholamine neurons in the CNS. In studies now initiated, we intend to investigate the anatomy of a number of new catecholamine systems--discovered with the glyoxylic acid method--in greater detail.